Análise do regime hidrológico e da disponibilidade hídrica da Bacia do Rio Amazonas

Abstract

The Amazon lives year after year the dynamics of Floods and lowing in its rivers. However, significant variability of river discharges in the face of historical series of climate data has become more persistent over the years. This study aims to analyze the influence of the temporal variability in the basin scale on the Amazon river regime, based on the flows observed in the hydrological station of the Agência Nacional de Águas - ANA, located in Óbidos, State of Pará, in a historical series of January / 1970 to December / 2013. Besides the time, the study analyzed the intensity of oceanic mechanisms on the Brazilian Amazon basin in each year of the series. As expected, time influenced the annual interannual flow rate of 98.723 m3/s for the 44 years of the analyzed series. However, the average flow rate of the Amazon River was around 134.000 m3/s, with a peak flow rate of 105.000 m3/s (as occurred in November) in the hydrological regime of effluent up to an order of 239.000 m3/s (as in June) in the flood regime. It was also identified that El Niño and La Niña phenomena modulated extreme climatic events causing negative and positive SST anomalies differentiated over the Amazon basin, between 1970 and 2013, with a significant relation in the effluent and flood flows. The interannual analysis showed that the years of low registered flows, had the characteristic of persistence of occurrence in relation to the registered high flows. At the end of the analyzed period, from 1989, there was a seasonal increase in relation to the average amplitude of the flow of 87.727 m3/s due to the strong minimum levels recorded. When analyzing the normalized flow, it was observed the persistence of low flow in the current year of the El Niño phenomenon and also of the following year. After verifying this below-average persistence of flow in the series studied, the research sought to investigate the storage and availability factors of the Amazon River. In determining the water availability of the Amazon River, the Percentis method (specifically the quantum order Q95%) was used. The analyzes of the available flows obtained by the 95% quantile show that the years of the El Niño phenomenon did not reflect the decrease in the flow of the Amazon River in all years of the series, since there were years of occurrence that did not present critical indices of water availability. It was concluded that the flow behavior in the Amazon basin was influenced by positive and negative SST anomalies modulated by the intensity of El Niño and La Niña, and there was not sufficient water availability for the maintenance of the ecosystems of the Amazon basin. Thus the study showed that naturally the annual flows of the Amazon River do not reach, in their totality, the minimum value determined for the historical series by the law. In addition to that the hydrological variabilities in the Amazon are not caused only by the phenomena of El Niño or La Niña.